Novel metasurfaces for mitigation of b₁ inhomogeneities in advanced metabolic mri at 7t clinical applications in neurodegenerative diseases Paul Samuel Jacobs

Format:

Book

Thesis/Dissertation

Author/Creator:

Jacobs, Paul Samuel, author.

Contributor:

University of Pennsylvania. Bioengineering., degree granting institution.

Language:

English

Subjects (All):

Medical imaging.

Biomedical engineering.

Neurosciences.

Biophysics.

0574.

0541.

0786.

0317.

Local Subjects:

Medical imaging.

Biomedical engineering.

Neurosciences.

Biophysics.

0574.

0541.

0786.

0317.

Genre:

Academic theses

Physical Description:

1 online resource (212 pages)

Contained In:

Dissertations Abstracts International 87-12B

Place of Publication:

Ann Arbor : ProQuest Dissertations and Theses, 2026

Language Note:

English

Summary:

Ultra-high field (≥7T) magnetic resonance imaging (MRI) offers superior spatial and spectral resolution but introduces challenges due to the shortened radiofrequency (RF) wavelengths. At 7T, the RF wavelength becomes comparable to human anatomy, causing constructive and destructive interferences, degrading image quality. While several post-processing methods have been introduced to mitigate these artifacts, they require additional scan time and do not address the problem optimally. Traditional dielectric padding has been used to mitigate these artifacts but has limited effectiveness, short shelf life, and are costly. Metamaterials have emerged as a promising alternative due to their enhanced electromagnetic control. Therefore, the goal of this thesis included developing flexible metasurfaces to improve RF coil transmit (B1+) field distribution in vivo at 7T, thereby enhancing image quality. We first began by assessing dielectric padding for metabolic imaging, specifically glutamate-weighted CEST (GluCEST) and nuclear Overhauser effect (NOEMTR) imaging and determined that they could be effectively used to correct these image types. The next experiment consisted of developing and performing initial safety validation of a prototype metasurface for use at 7T. We empirically optimized the metasurface design in which the surface impedance was adjusted to produce the maximum amount of phantom image SNR. In vivo testing in the calf and brain demonstrated substantial SNR increases in both anatomical and CEST-based imaging compared to reference acquisitions. A further aim was to translate these correction strategies into a clinical context. Dielectric pads were applied to improve NOEMTR imaging in a cohort of multiple sclerosis (MS) participants, enabling metabolic characterization of the disease. Imaging revealed decreases in global NOEMTR contrast, indicative of altered lipid metabolism. Overall, this work demonstrates the development of novel RF correction tools and their clinical application for enhancing metabolic and anatomical MRI. The findings support the use of metasurfaces as a viable means of overcoming field inhomogeneities and improving neuroimaging quality. These advances provide a foundation for future metasurface design and broader implementation in patient imaging studies

Notes:

Source: Dissertations Abstracts International, Volume: 87-12, Section: B.

Advisors: Reddy, Ravinder Committee members: Witschey, Walter; Detre, John; Schindler, Matthew; Brink, Wyger

Ph.D. University of Pennsylvania 2026

Vendor supplied data

Local Notes:

School code: 0175

ISBN:

9798247979395

Access Restriction:

Restricted for use by site license